1. Field of the Invention
The present invention relates to a field emission device and an image display device using the same.
2. Description of the Related Art
In order to find a substitute for the existing cathode ray tube (CRT), there has been vigorous research into development of flat panel displays, and the flat panel displays are being extensively developed to apply the same to a wall television and an image display for a high definition television (HDTV). Such flat panel displays include a liquid crystal device, a plasma display panel and a field emission device. Among those, much attention has been paid to the field emission device due to its brightness and low power consumption.
The conventional field emission device includes a cathode layer formed on a substrate in a predetermined pattern, microtips formed on the cathode layer, an insulation layer formed on the cathode layer to expose the microtips, and a gate electrode having an aperture exposing the microtips on the insulation layer.
If a predetermined voltage is applied between anodes (not shown) installed over the gate electrodes and microtips in a state where the microtips are grounded, electrons are emitted from the microtips. The field emission device has a short life because the microtips are susceptible to damage due to ion collision. Also, much electricity is consumed due to a high voltage for forming an electric field. A large amount of Joule heat is generated during electron emission, which may cause thermal deterioration of the device.
FIG. 1 illustrates an example of an image display device using a field emission device proposed for solving the problems of the conventional art.
As shown in FIG. 1, first and second electrodes 12 and 13 are formed to be spaced a predetermined distance apart from each other on the top surface of a rear substrate 11. Thin layers 14a and 14b formed of PdO are coated on the first and second electrodes 12 and 13, respectively. Also, a transparent front substrate 15 is coupled over the rear substrate 11 to form a free space for electron movement between the same and the rear substrate 11. A phosphor layer 16 and an accelerating electrode layer 17 are sequentially formed on the bottom surface of the front substrate 15.
In the operation of the field emission device 10 constructed as described above, a high voltage is applied to the accelerating electrode layer 17 and a predetermined voltage is applied to the first and second electrodes 12 and 13, so that electrons emitted between the thin layers 14a and 14b coated on the respective electrodes 12 and 13 are accelerated toward the accelerating electrode layer 17 to make the phosphor layer 16 luminesce.
However, the conventional field emission device has disadvantages in that it is difficult to maintain a small distance between thin layers 14a and 14b, for example to 10 nm, and there is a limit in selecting materials for forming thin layers and electrodes. Also, due to a complicated process for forming the thin layers, a large-screen image display device is difficult to fabricate.